Answer:
90% Confidence Interval = [24.81, 25.19]
Step-by-step explanation:
From the question, our number of samples is 20, it is small because it is less than 30. Hence we use the t score confidence interval formula
= Mean ± t score × Standard deviation/√n
Mean = 25 ohms
Standard deviation = 0.5 ohms
n = 20
We find the degrees of freedom = n - 1
= 20 - 1 = 19
Using the T score table
T score for 90% confidence interval with degrees of freedom 19
= 1.729
Hence:
Confidence Interval =
= 25 ± 1.729 × 0.5/√20
= 25 ± 0.1933080767
=
Confidence Interval
25 - 0.1933080767
= 24.806691923
≈ 24.81
25 + 0.1933080767
= 25.1933080767
≈ 25.19
90% Confidence Interval = [24.81, 25.19]
